Numerous types of conveyors are used in a variety of industries for material handling. Prior art conveyors include conveyor belts made of metal, plastic or other materials. These belts generally are flexible to enable them to negotiate curves or turns, and conventional systems employ a variety of constructions to achieve the desired flexibility.
Spiral style conveyor belts, for example, have a plurality of links movably mounted on transverse rods. This permits the belt to articulate as it negotiates a turn. When a conveyor belt negotiates a turn, the outer edge of the belt is subjected to tension. These tension loads have a resultant force that is directed toward the center of the turn radius. This resultant force is resisted by the belt and/or the rods on which the belt links are mounted, before being transposed to the structure supporting the belt in the turn. The tighter the turn, the higher the resultant force.
On many conveyor belts the links on the outer edge are made stronger to accommodate the tension loads in a turn, but unless the outer link is captured by some means it will migrate inward along the rod when subjected to the resultant force, and can cause bending of the rods when the resultant force is strong enough. Bending of the rods will cause the belt to bow and the edge of the belt to flip up. Moreover, permitting the outer link to migrate inward along the rod causes a number of other problems, including crushing of the inner modules or causing the inner modules to fail over time due to fatigue.
U.S. Pat. Nos. 4,949,838, 5,662,211, 6,213,292, 6,216,854, 6,237,750 and 6,345,715 are exemplary of some prior art arrangements in which the outer link is retained at the end of the rod to prevent the rod from moving outwardly through the link. However, these prior art arrangements rely upon a snap fit engagement, or a separate stop plate, or the link may be welded in place in the case of some metal belts, to retain the outermost link in position at the outer end of the rod. These arrangements may not be secure enough to resist the forces involved, whereby the link can become displaced from the end of the rod, and/or the use of separate parts is required, which increases the complexity and cost of assembling the belt.
Further, in those belts having links or modules movably mounted on spaced transverse rods, the rods typically have heads, or the rod may be grooved to accept a means of retention such as a clip or pin, or buttons formed on their ends to prevent the links from sliding off the rods. To enable assembly of the belts, the head or button generally is formed on one end of the rod, and the links are then slid onto the rod from the opposite end, after which a head or button is formed on that end. This can pose a problem in those belts wherein the links are made of plastic, since heat generally is applied to the end of the rod during forming of the head or button, and the heat can damage the adjacent link. Conventional belts having separate links or link modules movably mounted to transverse rods typically have both ends of the links fully captured, i.e., non-removably attached to adjacent rods, and do not have any means to enable the endmost link to be moved out of the way when heat is applied to the end of the rod during formation of the head or button.
In other conventional conveyor belt systems, the links are integrally formed with the rods, or if made of metal, welded to the rods. This arrangement clearly would prevent the links from migrating inwardly along the rods, and would obviate the necessity of forming heads or buttons on the ends of the rods, but it is very difficult, if not impossible, to alter the configuration of the belt, i.e., add or remove links, or adjust the width of the belt, etc.
In still other prior art constructions both ends of the links are removably attached to respective adjacent rods. While alteration of the belt geometry is easier to accomplish with this construction, there is a tendency for the links to become dislodged from the rods as the belt moves around a pulley or sprocket, or when engaged by a scraper.
Further, some prior art constructions attach the link to the end of the rod by welding, or a section or all of the plastic is completely removed to prevent heat damage to the plastic part. This allows the plastic part to become dislodged from the rods as the belt moves around a pulley or sprocket, or when engaged by a scraper.
Accordingly, there is need for a spiral style conveyor belt having separate links and link modules movably mounted on spaced transverse rods, wherein the outermost edge links are securely captured on the ends of the rods to prevent migration of the links inward along the rods when the belt negotiates a turn.
Further, there is need for a conveyor belt having separate links and link modules movably mounted on spaced transverse rods, wherein one end of at least some of the links is removably attached to the rod to enable the combined width of the links to be reduced to expose an end of the rod so that a head or button can be formed on the rod end without damaging the adjacent link.